Re: 6.6 L in-line & 160hp... would you purchase?
They were manufactured in Brazil by Ford's New Holland tractor division. Yes, they are a tractor engine, just as the Cummins 5.9 started life. I have not had to buy parts for mine other than filters and such which are stocked at any parts store worth a damn. Heck, I could probably even track down the part numbers if you wanted. I've just researched other parts like the water pump (after hearing a horror story from a guy) and found that A1 Cardone remans them and ASC makes them and I could get it overnight and for ~$150 I believe.
My local Ford dealer didn't have a lot of experience with them as they don't deal with a lot of medium duty trucks, but sure enough they had all the manuals and diagrams on microfiche and were more than helpful.
These trucks use a Bosch M-W inline injection pump which is pretty generic. It's similar though not the same as the much coveted P-Pump the Dodge guys love. The moral of the story is that it's extremely reliable, WVO-friendly, and you can turn up the power by adjusting some screws internal to it (there is obviously a limit to how far you can go). Write-ups galore exist on Google though one of our very own members has one of the best.
The 165 hp isn't going to hurt your top speed. It might make it a little tougher to maintain speed on long hills (the nemesis of any bus) but that's ok because it keeps other systems (like the turbo, transmission, and rear end) running happily at a reasonable temperature.